diff --git a/python/ppo/trainer.py b/python/ppo/trainer.py
index 8f1062a3bc..0227a65c21 100755
--- a/python/ppo/trainer.py
+++ b/python/ppo/trainer.py
@@ -122,7 +122,7 @@ def process_experiences(self, info, time_horizon, gamma, lambd):
                 else:
                     feed_dict = {self.model.batch_size: len(info.states)}
                     if self.use_observations:
-                        for i in range(self.info.observations):
+                        for i in range(len(info.observations)):
                             feed_dict[self.model.observation_in[i]] = info.observations[i]
                     if self.use_states:
                         feed_dict[self.model.state_in] = info.states